Gas turbine combustion chambers comprise a burner-side end and a turbine-side end. The turbine-side end is open and enables the hot combustion gases produced in the combustion chamber to flow out to the turbine. At the burner-side end a burner insert is often present which comprises a heat-resistant hot side and a cooled cold side. The burner is inserted into an opening in the burner insert. When the gas turbine is operating, cold air which as a rule comes from the compressor flows along the cold side from the burner opening of the burner insert to its outer edge, from where the cold air flows into the combustion chamber. An example of a burner insert in a can-type combustion chamber is described in US 2005/0016178 A1.
In the case of annular combustion chambers, in other words combustion chambers which extend in annular fashion around the turbine rotor, as a rule a plurality of burner inserts is arranged side by side in the circumferential direction of the annular combustion chamber. The cold air flowing past the cold side of the burner side then flows between the radially outer wall and the radially inner wall of the combustion chamber into the combustion chamber. In addition, cold air can also be introduced into the combustion chamber through gaps between adjacent burner inserts in the circumferential direction. Such an annular combustion chamber is described for example in EP 1 557 607 A1. Alternatively, it is also possible to direct the cold air towards the burner opening instead of away from the burner opening of the burner insert and then to introduce said cold air into the combustion chamber through an annular gap between the edge of the burner opening and the inserted burner, as is described in EP 1 767 855 A1.
A burner insert for an annular combustion chamber is illustrated schematically in FIG. 1. The figure shows a sectional perspective view of the cold side 103 of a burner insert for an annular combustion chamber. In the center of the cold side 103 of the burner insert 100 is situated an opening 105, into which the burner can be inserted. The burner insert is secured by means of an annular bar 107 in the section 109 of the burner insert 100 projecting beyond the cold side on a support structure in the gas turbine housing.
During operation of the gas turbine combustion chamber, pressure fluctuations may occur therein which can excite the burner insert to high-frequency oscillations. These stress the burner insert and shorten its useful life. In order to stiffen the burner insert and to direct the cold air, the cold side 103 of the burner insert 100 is provided with ribs 111. Furthermore, support bolts 113 are present, which are indicated only schematically in FIG. 1. The bolts 113 and the ribs 111 constitute contact sections by means of which the cold side comes into contact with the support structure in the gas turbine housing. With regard to such types of burner inserts, the formation of an uneven gap can occur along the circumferential edge of the burner insert, which can lead to an excess supply of cold air at points having an enlarged gap. Furthermore, on account of the fact that the support bolts 113 are also present in addition to the ribs 111, a static overdeterminacy results because the burner insert 100 should simultaneously bear both on the ribs 11 and also on the bolts.